368 ox TWO NEW CRTSTALLIXE COMPOUNDS 



I'affirnier, qu'elles sout, par compensation, en nombre moinclre, et que des differences 

 analogues ont lieu dans les autres CnSn, a mesure que ^ augmente jusqu'a ^ = go, ou 

 jusqu'a retain pur." It will be noticed that the difference between these needles is 

 precisely the same as the difference between the crystals of SbZng containing a small 

 and a large amount of zinc, and I think that no one, after reading Rieffel's paper, can 

 doubt that the compounds of copper or tin vary in composition like those of zinc and 

 antimony. 



2. The mineral Discrasite, a compound of silver and antimony, crystallizes in trimetric 

 prisms, of which I on I = 119° 59'.* The analyses given below are copied from 

 Dana's System of Mineralogy, changing slightly the order. 



SbAg3 = Antimony 28.5, Silver 71.5 = 100. SbAg^ = Antimony 23, Silver 77 = 100. 



1. Andreasberg (foliated granular) Antimony 24.25 Silver 75.25 = 99.5. Abich. 



2. Wolfach (coarse granular) " 24.00 ; " 76.00 = 100. Klaproth. 



3. Andreasberg (foliated granular) " 23.00 « 77.00 = 100. 



4. » " « « 22.00 " 78.00 = 100. Vauquelin. 



5. Wolfach (fine granular) « 16.00 " 84.00 =. 100. Klaproth. 



It needs no comment on these results to show that discrasite is homeomorphous with 

 SbZus, and varies like it in composition. 



3. In a paper recently published,t AY. Satorius von "SValterhausen, gives descriptions 

 and three analyses of a new mineral occurring with Dufrenoysite in the Binnen-V alley, 

 Switzerland, in Dolomite. As the analyses do not agree with each other and do not 

 correspond to a simple fonnula, von Walterhausen regards the compound as consisting 

 of two hypothetical isomorphous compounds, PbS + AsSg and 2 PbS + AsSg, and 

 calculates the proportions in which these compounds are mixed in the specimens ana- 

 lyzed. He infers that they are isomorphous, from their analogy in composition to 

 Zinkenite and Heteromorphite, PbS + SbSs and 2 PbS + SbSa, which he regards as iso- 

 morphous. Dr. J. D. Dana questions the isomorphism of the last, and thinks that the 

 hj^othesis that the new compounds are isomorphous requires further evidence. J 



4. It is stated by Staedeler,§ that crystals of the compound of grape-sugar and 

 common salt can be obtained containing for every equivalent of grape-sugar one or two 



* Dana's System of Mineralogy, 4th ed., Vol. II. p. 35. 

 t Poggendoif, Annalen, Vol. XCIV. p. 123. 

 f A7nerican Journal of Science, Vol. XIX. p. 355. 

 <J Chemical Gazette, Vol. XIII. p. 44. 



